Check for existing spaces gives false positive in migration assistant

Issue Summary

As part of the migration flow, the CCMA(Confluence Cloud Migration Assistant) needs to check if the selected spaces already exist in the target Cloud site to avoid errors during the import.

Right now, these checks might pass even though space already exists in the Cloud site with the same Space key you're migrating.

Steps to Reproduce

1. Create a Cloud space
2. Edit the Cloud space permissions so the site-admin user being used by CCMA doens't have the view permission on the Cloud space.
3. Create a server space with the same space key as the one in Cloud.
4. Create a new migration plan and migrate the Server space.

Expected Results

CCMA should be able to identify the existing space in the Cloud.

Actual Results

The Space key checks pass and the migration fails with Cloud site already has this space:

Workaround

Make sure the site-admin user has the required permissions in all Cloud spaces.
As a site admin, you can recover space permissions if needed.